Clean and gut a 3–4 lb burbot. Cut off the head, which is not served at the table. Pour wine vinegar over the fish and set aside for an hour. Boil 2 onions, ½ parsley root, half a handful of parsley, and 2–4 black peppercorns in water. Bring the broth to a rapid boil and add the fish. When the burbot has cooked, transfer it to a platter and garnish with parsley, the sliced burbot liver, and large, boiled crayfish. In a sauceboat, serve White sauce, Sauce, Field mushroom sauce, or Tomato sauce.
On meat days, it is good to serve the burbot with crayfish sauce.